Hot take: I used to overwork my sand mix and it cost me a lot of bad castings

For years I'd mix my silica sand and binder until it felt like a smooth dough. Thought more mixing meant better results. But last summer after a run of 15 cracked castings in a row at the shop in Gary, Indiana, I started paying attention. Turns out I was mixing too long and burning off the binder's moisture. My foreman finally said 'you're killing it, not helping it' and showed me to stop after 2 minutes flat. Now I mix just til the sand turns a uniform dark color and no more. I get less waste and way fewer repair jobs. Has anyone else found a specific mixing time that changed their pour quality?

2 comments

2 Comments

thea_chen3d ago

Buddy of mine wrecked a whole batch that way too.

evac723d ago

Oh man @thea_chen is right, I know someone who did the same thing. Honestly I had that exact same problem when I first started out. For months I was convinced more mixing time meant a better bond, but all I got was a ton of dry, crumbly sand that just fell apart in the flask. Tbh it wasn't until I watched a guy from an old foundry in Muncie show me his timer trick that it clicked for me. He said 'mix it til it's gray like a storm cloud, not black like asphalt' and that changed everything. Ngl I still catch myself wanting to go longer out of habit, but I force myself to stop at that two minute mark now. Saved me so many headaches with shrinkage and gas holes after that.